Angular 2 is written with TypeScript, but that doesn't mean we have to write our application with TypeScript. Angular 2 applications can be written with ES6 (JavaScript 2015) or even ES5 (JavaScript 1.5). In this book, we will use TypeScript, mainly (but not only) because of the implementations of decorators, which can clean our Angular 2 code compared to ES6 and ES5.
I will assume that you already know how to write JavaScript 2015 (ES6) code. Through this chapter, we will cover just what we need to know about TypeScript; most of the code is compatible with JavaScript 2015 as is. If you are not familiar with ES6 at all, it's highly recommended to catch up with the new syntax and features.
The following are the topics that we will cover:
An introduction to the TypeScript language
Manage dependencies with modules
Class declarations and usage
System, built-in, and custom types
How to use decorators